This invention relates to a night vision system for detecting objects at relatively low visible light levels. In particular, the invention relates to a night vision system utilizing a thin sheet optical element to emit infrared light and an infrared camera that detects the infrared light reflected off of objects in the environment.
Night vision systems are utilized to allow a user to see objects at relatively low visible light levels. Further, night vision systems may be classified as either passive night vision systems or active night vision systems. In known passive night vision systems used in automotive vehicles, mid-infrared cameras are used to image objects using the ambient infrared light emitted by the objects in the environment. Mid-infrared cameras generally used in automotive applications have a relatively small number of pixels. Accordingly, images formed using such cameras have a low video resolution and a relatively narrow field-of-view. Further disadvantages of night vision systems using mid-infrared cameras include (i) a relatively high manufacturing cost, (ii) generated images that are generally harder for a user to interpret than images formed using CCD or CMOS cameras, (iii) a potentially poor image contrast, and (iv) operational restrictions on the location of the camera resulting in a negative impact to the vehicle styling.
A known active night vision system utilizes an infrared diode laser or an incandescent light source and relatively large diameter lenses or reflectors to emit infrared light. The infrared light is subsequently reflected off objects in the environment and is received by an infrared camera. The infrared camera generates a video signal responsive to the received light. A disadvantage of the known active night vision system is that the lens or reflector-based illuminator package is relatively large. Accordingly, the known active system cannot be packaged in a small volume and placed on top of a dash or in a rear view mirror assembly of an automotive vehicle.
There is thus a need for a night vision system and a method related thereto that minimizes for reduces one or more of the above-mentioned deficiencies.
The present invention provides a night vision system and a method related thereto for detecting objects at relatively low visible light levels.
The night vision system in accordance with the present invention includes an infrared light source such as an infrared diode laser. The system further includes a thin sheet optical element extending along a first axis that receives light from the infrared light source and reflects the light generally in a first direction. Finally, the system includes an infrared camera for receiving the light reflected off of an object in the environment and generating a video signal responsive to the received light.
A method for detecting objects in accordance with the present invention includes a step of transmitting infrared light to a thin sheet optical element. The method further includes a step of reflecting the light from the thin sheet optical element generally in a first direction from the thin sheet optical element. The method further includes a step of receiving the light reflected off of an object in the environment. Finally, the method includes a step of generating a video signal responsive to the received light.
The night vision system and the method related thereto in accordance with the present invention represents a significant improvement over conventional systems and methods. In particular, the system may be packaged in a relatively small volume since the thin sheet optical element is extremely thin as compared with conventional lenses/illuminators. Accordingly, the inventive system may be located in a greater number of locations in an automotive vehicle. Further, the inventive system is less expensive, has a larger field-of-view, and provides higher quality images than known passive night vision systems.
These and other features and advantages of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.